The present invention relates to a core bar inserted to an elastic body of an elastic body track shoe used for an endless rubber crawler in a construction machine or the like.
An endless rubber crawler structured such that elastic body track shoes having core bars inserted to elastic bodies such as rubbers or the like are mounted at a predetermined interval via a pair of joint links and connection pins in a circumferential direction is frequently employed in a construction machine such as a hydraulic excavator or the like, and an industrial vehicle such as a crawler type conveyance vehicle or the like.
As a first conventional art of the elastic body track shoe, for example, there has been known a structure shown in FIG. 11. In FIG. 11, an elastic body track shoe 20 has an elastic body 22 such as a rubber or the like, and a core bar 21 inserted to the elastic body 22. The core bar 21 employs a reduction roll material cut in a predetermined shape, and is structured such that both end portions in a direction of width of a crawler belt (that is, both right and left wing portions) are inclined upward at a predetermined angle in a direction of a non-grounded surface and the other portions than both end portions in the direction of the crawler belt width are manufactured in the same cross sectional shape in a side view.
However, since the core bar 21 mentioned above is manufactured by the sheet material obtained by cutting the reduction roll material, there is provided the flat core bar 21 having the same thickness all around the portions except both end portions 21a and 21a in the direction of the crawler belt width which is chamfered in a manner shown in FIG. 11, and a weight thereof becomes heavy.
As a second prior art against the problem mentioned above, for example, there is a core bar for a rubber crawler disclosed in Japanese Patent No. 3033674, and FIGS. 12 and 13 are respectively inside plan view and a front elevational view of a core bar described in the publication. In accordance with the publication, thick portions 34 and 34 extending in a longitudinal direction of a core bar 31 are formed in front end portions of right and left wing portions 33 and 33 of the core bar 31, and there are disclosed a matter that a rib reinforcing effect is achieved by increasing a thickness of the thick portions 34 and 34 so as to form the core bar 31 in a shape protruding upward from the surface, a matter that a strength of a core bar is increased by forming the rib so as to achieve a light structure, and a matter that a plurality of hole portions 32 and 32 are provided in the right and left wing portions 33 and 33 for the purpose of improving an adhesion property between the core bar 31 and the rubber elastic body so as to achieve a light structure.
However, in the core bar for the rubber crawler disclosed in the publication, there is a problem that in a core bar lightening means forming the rib by protruding upward the front end portion of the core bar 31 from the surface and having an increased strength, an elastic deformation of the rubber elastic body adhered to the core bar 31 is restricted in a freedom of deformation at the portion of the protruded upward rib, and an elastic strain is concentrated so as to quicken a fatigue crack of the rubber elastic body.
Further, in the core bar lightening means having a hole pierced in the core bar 31, since a plurality of hole portions 32 and 32 are provided in both wing portions 33 and 33 of the core bar 31, there are problems that a strength of the core bars in both wing portions 33 and 33 is reduced and the rubber elastic body deformed due to the applied weight is in contact with an edge of the hole so as to be easily cut.
The present invention is made by taking into consideration a matter that a strength required in each of portions of a core bar is not uniform in all around the portions and a matter that the core bar is rigidly integrated via a crawler belt connection link and a link connection pin. Further, an object of the present invention is to provide the core bar of an elastic body track shoe structured such as to achieve a light structure by making a stress excess portion in the core bar thin, prevent an elastic body from strain deforming by forming a smooth rib reinforcing portion in which an edge portion of the core bar does not protrude from a core bar surface, secure a strength even when a hole is pierced in the core bar, and make the elastic body not be cut by an edge portion of the hole.
In order to achieve the object mentioned above, in accordance with a first aspect of the present invention, there is provided a core bar of an elastic body track shoe inserted to an elastic body such as a rubber or the like in the elastic body track shoe fastened to each pair of joint links of a crawler by bolts and formed in a substantially flat surface shape on both of front and back surfaces, wherein recess portions formed in a substantially inverse-trapezoidal shape are formed in non-grounded surface sides of right and left wing portions in a direction of a crawler width.
In accordance with the first aspect, since the recess portions are formed in the right and left wing portions of the core bar, it is possible to achieve a light structure and it is possible to reduce a manufacturing cost. Further, since the recess portions are formed in the non-grounded surface sides while grounded surface sides of the right and left wing portions are kept in the flat surfaces, the grounded surface sides of the core bar are formed in a shape having no stress concentration, and it is possible to widely improve a durability. Further, in an outer peripheral portion of the recess portion, since a non-recess portion (having the same thickness and strength as those before forming the recess portion) is left along the direction of the crawler width in both end portions in a longitudinal direction of the crawler, it is possible to secure a necessary strength. Further, since a surface changing to the recess portion from the non-recess portion on the flat surface is formed in a smooth surface having a substantially inverse-trapezoidal shape, it is possible not only to increase an adhesive strength with respect to the elastic body but also to avoid a concentration of elastic strain.
In accordance with a second aspect of the present invention, there is provided a core bar of an elastic body track shoe inserted to an elastic body such as a rubber or the like in the elastic body track shoe fastened to each pair of joint links of a crawler by bolts and formed in a substantially flat surface shape on both of front and back surfaces, wherein recess portions formed in a substantially inverse-trapezoidal shape open toward a front end portion are formed in non-grounded surface sides of right and left wing portions in a direction of a crawler width.
In accordance with the second aspect, since the recess portion open to the front end portion is formed in the non-grounded surface sides of the right and left wing portions in the core bar, it is possible to further lighten in comparison with the core bar in accordance with the first aspect, and it is possible to reduce a manufacturing cost. The other operations and effects are the same as those of the first invention.
In accordance with a third aspect of the present invention, there is provided a core bar of an elastic body track shoe inserted to an elastic body such as a rubber or the like in the elastic body track shoe fastened to each pair of joint links of a crawler by bolts and formed in a substantially flat surface shape on both of front and back surfaces, wherein a recess portion formed in a substantially inverse-trapezoidal shape is formed in a center portion in a direction of a crawler width.
In accordance with the third aspect of the present invention, since the recess portion is formed in the center portion in the direction of the crawler width of the core bar, it is possible to lighten the core bar, and it is possible to reduce a manufacturing cost. Further, since a pair of right and left joint links are connected to the center portion of the core bar and each pair of joint links are connected to each other by pins in an endless manner, the center portion of the core bar is structured in a box shape and a rigidity thereof is high, so that it is possible to maintain a sufficient strength even when the recess portion is provided in the center portion. Further, since the surface changing to the recess portion from the non-recess portion of the flat surface is formed in the smooth surface having the inverse-trapezoidal shape, it is possible not only to increase an adhesive strength with respect to the elastic body but also to avoid the concentration of the elastic strain.
In accordance with a fourth aspect of the present invention, there is provided a core bar of an elastic body track shoe inserted to an elastic body such as a rubber or the like in the elastic body track shoe fastened to each pair of joint links of a crawler by bolts and formed in a substantially flat surface shape on both of front and back surfaces, wherein a through hole is formed in a center portion in a direction of a crawler width.
In accordance with the fourth aspect of the present invention, since the through hole is formed in the center portion in the direction of the crawler width of the core bar, it is possible to further lighten the core bar in comparison with the third aspect, and it is possible to reduce a manufacturing cost. At this time, since a pair of joint links, the connection pin and the core bar are rigidly integrated and the center portion of the core bar is structured in the box shape as described in the third aspect, it is possible to secure a sufficient strength of the core bar even when the through hole is pieced in the center portion of the core bar. Further, in order to prevent the elastic body from deforming so as to be in contact with the edge portion of the through hole pieced in the core bar, thereby being cut, the structure is made such that a through hole is formed in a portion of the elastic body at the same position as the hole of the core bar, whereby the elastic body is not in contact, or a recess portion is formed in a grounded surface of the center portion in the elastic body so as not to be grounded, whereby an elastic deformation due to a load application is not given, so that the problem can be achieved.
Further, since a water and a muddy water are discharged from the through hole by providing the through hole in the elastic body at the same position as this through hole, thereby reducing earth and sands attached to the core bar, it is possible to improve a durability of the track shoe of the elastic body. The other operations and effects are the same as those of the third aspect.
In accordance with a fifth aspect of the present invention, there is provided a core bar of an elastic body track shoe inserted to an elastic body such as a rubber or the like in the elastic body track shoe fastened to each pair of joint links of a crawler by bolts and formed in a substantially flat surface shape on both of front and back surfaces, wherein recess portions formed in a substantially inverse-trapezoidal shape are formed in non-grounded surface sides of right and left wing portions in a direction of a crawler width, and a recess portion formed in a substantially inverse-trapezoidal shape is formed in a center portion in the direction of the crawler width.
In accordance with the fifth aspect, the same operations and effects as those of the first and third aspects can be obtained.
In accordance with a sixth aspect of the present invention, there is provided a core bar of an elastic body track shoe inserted to an elastic body such as a rubber or the like in the elastic body track shoe fastened to each pair of joint links of a crawler by bolts and formed in a substantially flat surface shape on both of front and back surfaces, wherein recess portions formed in a substantially inverse-trapezoidal shape are formed in non-grounded surface sides of right and left wing portions in a direction of a crawler width, and a through hole is formed in a center portion in the direction of the crawler width.
In accordance with the sixth aspect, the same operations and effects as those of the first and fourth aspects can be obtained.
In accordance with a seventh aspect of the present invention, there is provided a core bar of an elastic body track shoe inserted to an elastic body such as a rubber or the like in the elastic body track shoe fastened to each pair of joint links of a crawler by bolts and formed in a substantially flat surface shape on both of front and back surfaces, wherein recess portions formed in a substantially inverse-trapezoidal shape open toward front end portions are formed in non-grounded surface sides of right and left wing portions in a direction of a crawler width, and a recess portion formed in a substantially inverse-trapezoidal shape is formed in a center portion in the direction of the crawler width.
In accordance with the seventh aspect, the same operations and effects as those of the second and third aspects can be obtained.
In accordance with an eighth aspect of the present invention, there is provided a core bar of an elastic body track shoe inserted to an elastic body such as a rubber or the like in the elastic body track shoe fastened to each pair of joint links of a crawler by bolts and formed in a substantially flat surface shape on both of front and back surfaces, wherein recess portions formed in a substantially inverse-trapezoidal shape open toward front end portions are formed in non-grounded surface sides of right and left wing portions in a direction of a crawler width, and a through hole is formed in a center portion in the direction of the crawler width.
In accordance with the eighth aspect, the same operations and effects as those of the second and fourth aspects can be obtained.